I purchased 4 yards of this fabric. It's only 45" wide so I'm probably going to have to cut & stitch the fabric to make it wider. Should i cut & Stitch so that the seam runs in the center from front to rear? Or should i do it so it runs from side to side? Will it look like crap with a seam?

Is 45" wide enough? That fabric right there is folded in half & rolled.

I don't think that seams look good in anything except leather.... but that's just me. If it were me and I was doing this, I would stitch from left to right and put the seam just above and just behind the headrests on the seats.

Do you already have an anthracite headliner? If not what are you going to do about your sunvisors/sunroof/sunroof switch?

I would run it up the middle over side to side. It is what we do at the shop I work at, but only if the material is to narrow. You really should consider using the correct size material. No matter what, with a seam it is going to be difficult to get it to look good and be straight.